# HD44780 LCD Test Script for
# Raspberry Pi

#import
import RPi.GPIO as GPIO
import time, sys

# Define GPIO to LCD mapping
LCD_RS = 18
LCD_E  = 17
LCD_D4 = 22 
LCD_D5 = 23
LCD_D6 = 24
LCD_D7 = 25
LCD_BACKLIGHT = 7

# Define some device constants
LCD_WIDTH = 20    # Maximum characters per line
LCD_CHR = True
LCD_CMD = False

LCD_LINE_1 = 0x80 # LCD RAM address for the 1st line
LCD_LINE_2 = 0xC0 # LCD RAM address for the 2nd line 
LCD_LINE_3 = 0x94 # LCD RAM address for the 3rd line
LCD_LINE_4 = 0xD4 # LCD RAM address for the 4th line

lines = [LCD_LINE_1, LCD_LINE_2, LCD_LINE_3, LCD_LINE_4]

# Timing constants
E_PULSE = 0.00005
E_DELAY = 0.00005

def gpio_init():
  GPIO.setwarnings(False)
  GPIO.setmode(GPIO.BCM)       # Use BCM GPIO numbers
  GPIO.setup(LCD_E, GPIO.OUT)  # E
  GPIO.setup(LCD_RS, GPIO.OUT) # RS
  GPIO.setup(LCD_D4, GPIO.OUT) # DB4
  GPIO.setup(LCD_D5, GPIO.OUT) # DB5
  GPIO.setup(LCD_D6, GPIO.OUT) # DB6
  GPIO.setup(LCD_D7, GPIO.OUT) # DB7
  GPIO.setup(LCD_BACKLIGHT, GPIO.OUT)
  time.sleep(0.5)
  GPIO.output(LCD_BACKLIGHT, False)
  time.sleep(0.5)

def lcd_init():
  # Initialise display
  lcd_byte(0x33,LCD_CMD)
  lcd_byte(0x32,LCD_CMD)
  lcd_byte(0x28,LCD_CMD)
  lcd_byte(0x0C,LCD_CMD)  
  lcd_byte(0x06,LCD_CMD)
  lcd_byte(0x01,LCD_CMD)  
  time.sleep(0.1)
  backlight_on()

def display(line, string):
    lcd_byte(lines[line], LCD_CMD)
    lcd_string(string)

def clear():
    for line in range(0,3):
        display(line," "*20)
        
def lcd_string(message):
  # Send string to display

  message = message.ljust(LCD_WIDTH," ")  

  for i in range(LCD_WIDTH):
    lcd_byte(ord(message[i]),LCD_CHR)

def lcd_byte(bits, mode):
  # Send byte to data pins
  # bits = data
  # mode = True  for character
  #        False for command

  GPIO.output(LCD_RS, mode) # RS

  # High bits
  GPIO.output(LCD_D4, False)
  GPIO.output(LCD_D5, False)
  GPIO.output(LCD_D6, False)
  GPIO.output(LCD_D7, False)
  if bits&0x10==0x10:
    GPIO.output(LCD_D4, True)
  if bits&0x20==0x20:
    GPIO.output(LCD_D5, True)
  if bits&0x40==0x40:
    GPIO.output(LCD_D6, True)
  if bits&0x80==0x80:
    GPIO.output(LCD_D7, True)

  # Toggle 'Enable' pin
  time.sleep(E_DELAY)    
  GPIO.output(LCD_E, True)  
  time.sleep(E_PULSE)
  GPIO.output(LCD_E, False)  
  time.sleep(E_DELAY)      

  # Low bits
  GPIO.output(LCD_D4, False)
  GPIO.output(LCD_D5, False)
  GPIO.output(LCD_D6, False)
  GPIO.output(LCD_D7, False)
  if bits&0x01==0x01:
    GPIO.output(LCD_D4, True)
  if bits&0x02==0x02:
    GPIO.output(LCD_D5, True)
  if bits&0x04==0x04:
    GPIO.output(LCD_D6, True)
  if bits&0x08==0x08:
    GPIO.output(LCD_D7, True)

  # Toggle 'Enable' pin
  time.sleep(E_DELAY)    
  GPIO.output(LCD_E, True)  
  time.sleep(E_PULSE)
  GPIO.output(LCD_E, False)  
  time.sleep(E_DELAY)   
  
def is_backlight_on():
    return backlight_is_on
    
def backlight_on():
    global backlight_is_on
    backlight_is_on = True
    GPIO.output(LCD_BACKLIGHT, True)
    print 'backlight on'
    
def backlight_off():
    global backlight_is_on
    backlight_is_on = False
    GPIO.output(LCD_BACKLIGHT, False)
    print 'backlight off'
